As electronic circuits and systems are becoming ever more popular in critical applications, including, but not limited to, data storage, electronic vehicles and aeronautics, so do their operating conditions become harsher. This often means using electronic components at or near the limit of their functional parameters and very close to or even exceeding their maximum operating temperature. Accurately monitoring the temperature of these electronic circuits and systems therefore becomes critical to avoiding failures or other reliability issues.
In certain temperature measurement applications, such as, for example, monitoring the temperature of a hard disk drive so as to change temperature-sensitive parameters relating thereto, a thermistor is often placed at the disk drive head. A thermistor is a well-known type of device having a resistance that varies significantly with temperature, more so than in standard resistors. A voltage across the thermistor is measured and a corresponding temperature is obtained (e.g., based on a prescribed relationship between temperature and resistance associated with the device) as a function of the voltage across the thermistor.
There are many sources of error using this standard approach. Two primary sources of error are the variation in the external voltage supply, which is typically used to bias the thermistor, and the accuracy of an internal voltage reference often used for comparison with the thermistor voltage. To reduce these errors, a calibration procedure can be employed, such as during power-up. However, calibration increases circuit complexity and must generally be performed by the user, and is therefore undesirable. Furthermore, because calibration is typically only performed once (e.g., at power-up), such an approach cannot correct errors resulting from variations in temperature or other operating conditions which occur after calibration has completed.